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Peter Anvin" , Arnd Bergmann , Greg Kroah-Hartman , Dan Williams , Vishal Verma , Dave Jiang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Tvrtko Ursulin , Christian Koenig , Huang Rui , Matthew Auld , Matthew Brost , Alexander Viro , Christian Brauner , Jan Kara , Benjamin LaHaise , Gao Xiang , Chao Yu , Yue Hu , Jeffle Xu , Sandeep Dhavale , Hongbo Li , Chunhai Guo , Theodore Ts'o , Andreas Dilger , Muchun Song , Oscar Salvador , David Hildenbrand , Konstantin Komarov , Mike Marshall , Martin Brandenburg , Tony Luck , Reinette Chatre , Dave Martin , James Morse , Babu Moger , Carlos Maiolino , Damien Le Moal , Naohiro Aota , Johannes Thumshirn , Matthew Wilcox , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Hugh Dickins , Baolin Wang , Zi Yan , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Jann Horn , Pedro Falcato , David Howells , Paul Moore , James Morris , "Serge E . Hallyn" , Yury Norov , Rasmus Villemoes , linux-sgx@vger.kernel.org, linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-erofs@lists.ozlabs.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org, ntfs3@lists.linux.dev, devel@lists.orangefs.org, linux-xfs@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH RESEND 09/12] mm: make vm_area_desc utilise vma_flags_t only Message-ID: <20260120133619.GZ1134360@nvidia.com> References: <20260119231403.GS1134360@nvidia.com> <36abc616-471b-4c7b-82f5-db87f324d708@lucifer.local> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <36abc616-471b-4c7b-82f5-db87f324d708@lucifer.local> X-ClientProxiedBy: BLAPR03CA0176.namprd03.prod.outlook.com (2603:10b6:208:32f::26) To LV8PR12MB9620.namprd12.prod.outlook.com (2603:10b6:408:2a1::19) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: LV8PR12MB9620:EE_|IA0PR12MB8325:EE_ X-MS-Office365-Filtering-Correlation-Id: 2d561cbc-87a7-4e6a-629c-08de5828e547 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|1800799024|7416014|376014; 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Seems like it > > might invite some negative optimizations since now the compiler has to > > optimze away a copy too. > > I really don't think so? This is inlined and thus collapses to a totally > standard vma_flags_test_all() which passes by value anyway. > Do you have specific examples or evidence the compiler will optimise poorly here > on that basis as compared to pass by reference? And pass by reference would > necessitate: I've recently seen enough cases of older compilers and other arches making weird choices to be a little concerened. In the above case there is no reason not to use a const pointer (and indeed that would be the expected idomatic kernel style), so why take chances is my thinking. Jason